Electrical connecter



July 16, 1935. i c. w. BLOUNT 2,008,573

ELECTRICAL CONNECTER Filed June 8, 1929 4 ,5 J5 7MOLDED RES/NO/D Z/COMPOS/T/ON i /0 55 f v/ rem/0 30 50 1 A? SUBSTANCE. j 4- M/CA wsumT/a/vINVENTOR RNEY Patented July 16, 1935 PATENT OFFICE 2,003,513 ELECTRICALcomcrnn Clinton W. Blount, Newark, N. J., assignor to BakeliteCorporation, New York, N. Y., a corporation of Delaware Application June8, 1929, Serial No. 369,305

2 Claims. (Cl. 173-269) Thisinvention relates to connecters establishingcontacts between conductors or cable ends and electrical apparatus forthe transmission of electrical currents. The invention is hereinafterset 5 forth in its application to high tension leads to the spark plugsof an internal combustion, particularly an airplane motor, but it is tobe understood that it is of general application commensurate with thescope of the appended claims.

A number of problems arise in connection with supplying of current tothe spark plugs of an engine. For instance a mechanically strongconnection is required that will not loosen or break on account of thevibrations. Again as the current is supplied under voltages of over20,000, it is highly desirable that the contact be. insulated in such amanner as to prevent dissipation through leakage paths; such insulationis more particularby required when the spark plugs are shielded toovercome interference with the reception and sending of radio. Anotherfactor that must generally be taken into consideration is the limitedspace available for making the connection. There is furthermore therelatively high temperature caused by the release of heat during theengine operation, which may be as high as 350 to 375 F. at the outer endof the spark plug.

A construction that has been proposed for a spark plug connectercomprises an insulating elbow, one arm of the elbow contacting a sparkplug and enclosing a conductor from the spark plug and the other armenclosing a cable lead. As the spark plug is provided with a metal shellwhich is grounded, a short air-gap from the conductor to the shell ispresent if the elbow rests upon the upper surface of the plug. Such anair gap is obviated by extending the insulating elbow into the sparkplug since a material of high insulating value, such as mica, lines theinterior of the spark plug shell. The elbow is preferably molded from asynthetic phenolic resinoid composition, that is, a compositionincluding as a binder a product obtained in the reaction of a phenol andformaldehyde or equivalent methylene-containing agent and characterizedby a transformation from an initial fusible and reactive state to afinal infusible one upon heating. These phenolic resinoid compositionsin their final reacted condition have a good mechanical strength and arehighly desirable as electrical insulation; but, while they are infusibleand do not soften under high temperatures, their loss in strength andelectrical properties at the high temperatures that are apt to bepresent is found obiectionable.

According to the present invention this disadvantage of the priorconstruction is overcome by substituting a vitrified inorganicsubstance, as porcelain, for the extension of the connecter while thephenolic resinoid composition is retained for the remainder of the elbowstructure, thus combining the mechanical strength and other propertiesof the resinoid for the exterior exposed portion of the connecter andthe insulating-property at high temperatures for the inclosed protected10 portion.

In the accompanying drawing the figure is a vertical cross sectionthrough a connecter and the outer end of a shielded spark plug.

The connecter as illustrated comprises a hollow member 1 with arms 2 and3 and molded preferably from a composition consisting of a phenolicresinoid and a finely sub-divided filler which may be wood flour,asbestos, mica or other suitable material. The arm 2 is provided with a20 passage 4 large enough to receive the end of an insulated cable 5,and the other arm 3 likewise has a passage 6 opening into the passage 4.

The end surface 1 of the arm 3 is intended to contact the exposed endIII of a spark plug ll. 25 The spark plug is made with a' metal shieldor shell I! which is grounded but also acts to prevent high tensionradiation aifecting the reception and transmission of radio waves; thisshell encloses an annular mica insulation l4, forming 30 a cylindricaldepression l5 in the upper or exposed end of the spark plug.

A central contact I6 is provided at the bottom of the depression of thespark plug for a conductive element 20, or the conductive element can bemade integral with the contact. This conductive element projects fromthe depression and is long enough to extend through the passage 6 of theconnecter and to firmly grip the exposed conductor end 2| of the lead-incable 5 against 40 the wall of the passage in the arm 2 when theconnecter or elbow is seated on the surface H of the plug.

As shown, the insulation forming the extension is a porcelain tube 30about the conductive 45 element 20 fitting into the cylindricaldepression ii of the spark plug and into the elbow. The contact 3| withthe elbow is corrugated, made helical or otherwise formed to give anenlarged surface contact. By this arrangement a 50 double function isprovided: an adequate grip on the porcelain is afforded the resinoidinsulation of the elbow-and the surface is greatly extended thusproviding a greatly increased leakage path from the element 20 to theshell l2. The soincreased leakage path permits a material reduction inthe length of the porcelain tube and adapts it for limited spaces.

The elbow can be secured to the spark plug by any suitable clampingmeans. That illustrated is the ordinary pipe union consisting of theswivel nut 32 held in place by a flange 33 on the spark plug andengaging screw threads 34 on the elbow. The elbow is preferably coveredwith a shielding 35 made of woven wire or other suitable material.

I claim:

1. A connecter for establishing contact between an electrical conductorand electrical apparatus having a depression in its contact surface anda conductive element extending through and projecting from thedepression comprising in combination a shielded insulating member moldedfrom a resinoid composition and enclosing the conductor at one end,insulation formed from a vitrified substance projecting from the otherend of said member and conformed to fit the depressionin the apparatus,and clamping means external of said members for securing intimatecontact between said conductive element and th conductor end.

2. A connecter for establishing contact between an electrical conductorand electrical apparatus having a depression in its contact surface anda conductive element extending through and projecting from thedepression comprising in combination an insulating member molded from aphenolic resinoid composition enclosing the conduct0r at one end; ahollow porcelain insulation extending from the other end of said memberinto the depression and about the conductive element, the contactingsurfaces of said member and said insulation having a sinuousconformation, and clamping means external 0! said member for securingintimate contact between said conductive element and the conductor end.

CLINTON W. BLOUN T.

